Earthing Points

Hi

I went to one RMG(Ring main gear) service for maintenance.They are availing EB supply and they are having one genset for alternate supply with AMF panel.

They switched off EB supply and availed generator supply.Then they told you start your maintenance work.

Then we start to measure earth pit resistance after disconnecting all earth plates connected to earth pit.

Now I have one doubt.that is generaor neutral is seperately earthed or earthed with station earth pit networks.I discussed with that station operator,they told that generator neutral is seperately earthed.

i want to know what is the principle behind it.how it should be?

please share your views.

regards

gova